A5.018 gram sample of a certain hydrate of magnesium sulfate, mgso4•xh2o, is heated until all the water is driven off. the resulting anhydrous compound weighs 2.449 grams. what is the formula of the hydrate?

Hydrate of magnesium sulphate undergoes dehydration upon action of heat. This process can be chemically represent as follows:

MgSO4.XH2O  → MgSO4 + XH20
       (5.018 g)      (2.449 g)     (2.569 g)

Number of moles of H2O evolved = 
                                                      = 
                                                      = 0.1427
Number of moles of MgSO4 generated after decomposition,
= 
=
=0.0203

Now dividing  both these numbers by the smallest one to get the mole ratio that exists between MgSO4 and H20

For H2O,  = 7.02 ~7

Thus, formula of hydrate is MgSO4.7H2O